The embodiments described herein relate generally to gas turbine engines, and more particularly, to methods and systems for extracting and controlling cooling flow from a compressor to a turbine for improving the efficiency and/or operation of the gas turbine engine.
Typically, gas turbine engines include a compressor, a combustor, and a turbine. The compressor and turbine may include rows of blades that are axially stacked in stages. Each stage includes a row of circumferentially-spaced stator blades, which are fixed, and a row of rotor blades, which rotate about a central axis or shaft. In operation, the compressor rotor blades rotate about the shaft, and, acting in concert with the stator blades, compress a flow of air. The supply of compressed air then may be used in the combustor to combust a supply of fuel. Moreover, the resulting flow of hot gases from the combustion, i.e., the working fluid, is expanded through the turbine section of the engine. Conventionally, the flow of working fluid through the turbine induces the rotor blades to rotate. The rotor blades are connected to a central shaft such that the rotation of the rotor blades rotates the shaft for work output.
More particularly, the energy contained in the fuel may be converted into the mechanical energy of the rotating shaft, which, for example, may be used to rotate the rotor blades of the compressor, such that the supply of compressed air needed for combustion is produced, and for the coils of a generator, such that electric power is generated. During operation, because of the extreme temperatures of the hot-gas path, which may exceed 2400° F. (1316° C.), and high rotational velocities, turbine blades may be highly stressed with mechanical and thermal loads. Some turbine engines may extract air from the compressor to cool components in the hot-gas path during operation. This air extraction comes at an efficiency price, however, as the usage of compressor air in this manner may decrease the efficiency of the turbine engine.
To improve gas turbine efficiency and/or reduce fuel consumption, the amount of air extracted, or bled, from the compressor should be reduced. A conventional method of reducing bleed air may include reducing the temperature of the bleed air since less air may be required to perform the same amount of cooling. To reduce the cooling air temperatures, some gas turbines may use heat exchangers such that a cooler side of the heat exchanger is in flow communication with a cooler external air stream. The addition of heat exchangers, however, may increase the cost and/or weight of the turbine engine and increase the bypass duct pressure loss which may negatively affect fuel consumption. Moreover, some gas turbines may use blade cooling techniques such as film-holes, impingement baffles and serpentine structures. These techniques, however, may add to manufacturing, operational, and/or maintenance costs.